Thermocouples have long been used as temperature measuring devices. A thermocouple consists of a pair of conductors made of different materials which are joined together and contact each other at each end and otherwise insulated from one another along their lengths. Each junction thus formed produces a thermal emf or thermal voltage between the dissimilar conductors which is a function of its temperature. Such a thermocouple may be used as an electronic sensor to monitor temperature by cutting one of the conductors and inserting a voltage measuring device between the cut ends. The voltage which appears at the cut ends and is therefore measured by the voltmeter is a function of the difference in temperature between the two thermocouple junctions. By maintaining one of the junctions (the reference junction) at a known reference temperature, the other junction (the measuring junction) will function as a probe which monitors its local temperature with respect to the reference temperature.
It is often desirable to make temperature measurements at a number of different points in a region of space. A one-dimensional array of thermocouple measuring junctions can be built by contacting, at intervals along a length of one conductor made of a first material (e.g. Metal "A") a series of separate junction branches, each composed of another conductor made of a dissimilar material (e.g. Metal "B"). To measure the temperature at a selected junction, the Metal "B" branch of the selected junction can be switched to the voltmeter. However, in doing so care must be taken to avoid having more than one thermocouple junction active in the circuit at any time. If two or more thermocouple branches are electrically connected in parallel, each will interfere with the others' voltage output, resulting in a gross loss of localized thermometric accuracy.
For this reason, it has been impossible to extend the technique of such a simple linear array into a two-dimensional simple grid mesh of thermocouple junctions. Until now, the only solution to building a two-dimensional array of thermocouple elements was to create a two-dimensional branched or meander linear array. Design and construction of such an array, even of modest size, can be physically and electrically cumbersome. For an array of M rows by N columns of elements, M x N junction branches need to be laid out and separately addressed. For instance, for a 10.times.10 array, 100 branches are required to be separately addressed.